Substrate cleaning method, cleaning solution, cleaning apparatus and semiconductor device

Abstract

Disclosed is a substrate cleaning method for removing particles from a substrate includes a first step of adjusting the concentration of dissolved nitrogen in pure water, so as to be less than or equal to the concentration of dissolved nitrogen in equilibrium with the atmosphere (about 16 ppm), in a supply line that supplies the pure water, and a second step of cleaning a substrate by supplying a cleaning tank with a cleaning solution produced by mixing at least hydrogen peroxide with the pure water adjusted at the first step, and applying an ultrasonic wave to the cleaning solution in which the substrate is immersed.

Description

[0001] This invention relates to a cleaning method, cleaning solution and cleaning apparatus for cleaning a substrate by application of ultrasonics, and to a semiconductor device that has been cleaned by the cleaning method. More particularly, the invention relates to a substrate cleaning method, cleaning solution and cleaning apparatus exhibiting a high particle removing capability with regard to particles adhering to a substrate, and to a semiconductor device cleaned by this cleaning method.[0002] According to a conventional cleaning technology, particles and the like adhering to a substrate such as a semiconductor substrate, liquid-crystal glass substrate or magnetic disk are removed by immersing the substrate in a cleaning solution accommodated in a cleaning tank and applying ultrasonic waves to the substrate.[0003] The conventional method (ultrasonic cleaning method) of cleaning a semiconductor substrate will be described with reference to the drawings.[0004] As shown in FIG. 6...

AI Technical Summary

Benefits of technology

[0013] An inert gas such as nitrogen is dissolved beforehand in pure water that is supplied. This is to prevent oxygen from dissolving in the pure water in the process of delivering the pure water to the cleaning tank.

[0017] According to another aspect of the present invention, the foregoing object is attained by providing a method of cleaning a substrate comprising a first step of adjusting concentration of dissolved nitrogen in pure water, so as to be less than or equal to concentration of dissolved nitrogen in equilibrium with the atmosphere (about 16 ppm), in a pure-water supply line that supplies the pure water; and a second step of cleaning a substrate by supplying a cleaning tank with a cleaning solution produced by mixing hydrogen peroxide and ammonia with the pure water adjusted at the first step, and applying an ultrasonic wave to the cleaning solution in which the substrate has been immersed. This method makes the hydrogen peroxide function even in a case where APM solution (a solution that is a mixture of NH.sub.4OH, H.sub.2O.sub.2 and pure water) is used. It should be noted that since ammonia exhibits strong hydrogen bonding with respect to water, almost no bubbling of ammonia due to the application of an ultrasonic wave (megasonics) occurs.

[0020] In the substrate cleaning method set forth above, the concentration of dissolved nitrogen in pure water prior to the adjustment in the first step preferably is the concentration (about 16 ppm) of dissolved nitrogen in pure water in a state of equilibrium with the atmosphere. This is to prevent the dissolution of harmful oxygen in the process of delivering the pure water prior to adjustment.

[0022] According to a further of the present invention, the foregoing object is attained by providing a cleaning solution including pure water and hydrogen peroxide, wherein the pure water is such that concentration of dissolved nitrogen has been adjusted so as to be less than concentration of dissolved nitrogen in equilibrium with the atmosphere. Owing to the combination of the hydrogen peroxide with pure water, the hydrogen peroxide, which is vital for the cleaning process, is made to function. Preferably, the concentration of dissolved nitrogen in pure water after adjustment is 10 to 16 ppm. This is to induce bubbling of the hydrogen peroxide sufficiently without the occurrence of standing waves so that cleaning can be performed evenly and efficiently.

[0025] In the cleaning apparatus described above, the measurement unit and the degassing unit preferably are placed in the pure-water supply line in close proximity to the mixer. This is to suppress the dissolution of harmful oxygen in the process of delivering the pure water after to adjustment.

Problems solved by technology

However, even if the concentration of dissolved nitrogen gas in pure water used in an APM solution or the like is controlled by the conventional method, it is difficult to achieve the cleaning ability sought for the substrate cleaning fluid by employing the solutions of the aforementioned type.

The result is inactivity of the cleaning-solution molecules, a failure to increase the number of volatile bubbles produced by the H.sub.2O.sub.2 molecules and a failure to achieve an efficacious particle removal effect.

Images